Strategies for preparation of chitosan based water-soluble fluorescent probes to detect Cr3+ and Cu2+ ions.

The low solubility of chitosan (CS) imposes adverse effects on its application. In this work, one of the aims is to improve the water solubility of CS. By introducing water-soluble side chains to CS, this aim was achieved. Besides, fluorescent moieties were incorporated into the side chains, the fluorescent copolymers were endowed with Cr3+ and Cu2+ ions recognition ability. Firstly, a reversible addition-fragmentation chain transfer polymerization (RAFT) reagent with naphthalimide units and CC groups was prepared. Water-soluble monomer methyl acrylic acid (MAA) was employed in the RAFT polymerization. Thus, water-soluble polymer with fluorescent unit and -C ≡ C on both ends of the polymer was obtained. They were introduced into CS, and the CS-based fluorescent copolymers were obtained eventually. The amount of MAA introduced could be tuned to obtain three side chains of different lengths. It was found that the more MAA was introduced, the better the solubility of CS-TP was. The detection limits (LOD) of Cr3+ and Cu2+ were 44.6 nM and 54.5 nM, respectively. The detection of Cr3+ and Cu2+ ions is further combined with a mobile APP to realize real-time, portable, and visual detection. And the application in the logic gate, a new detection platform, is prepared.

Synthesis of dendrimer-type chiral stationary phases based on the selector of (1S,2R)-(+)-2-amino-1,2-diphenylethanol derivate and their enantioseparation evaluation by HPLC.

In our recent work, a series of dendritic chiral stationary phases (CSPs) were synthesized, in which the chiral selector was L-2-(p-toluenesulfonamido)-3-phenylpropionyl chloride (selector I), and the CSP derived from three-generation dendrimer showed the best separation ability. To further investigate the influence of the structures of dendrimer and chiral selector on enantioseparation ability, in this work, another series CSPs (CSPs 1-4) were prepared by immobilizing (1S,2R)-1,2-diphenyl-2-(3-phenylureido)ethyl 4-isocyanatophenylcarbamate (selector II) on one- to four-generation dendrimers that were prepared in previous work. CSPs 1 and 4 demonstrated the equivalent enantioseparation ability. CSPs 2 and 3 showed the best and poorest enantioseparation ability respectively. Basically, these two series of CSPs exhibited the equivalent enantioseparation ability although the chiral selectors were different. Considering the enantioseparation ability of the CSP derived from aminated silica gel and selector II is much better than that of the one derived from aminated silica gel and selector I, it is believed that the dendrimer conformation essentially impacts enantioseparation.

Immobilization of (1S,2R)-(+)-2-amino-1,2-diphenylethanol derivates on aminated silica gel with different linkages as chiral stationary phases and their enantioseparation evaluation by HPLC.

A chiral selector was prepared through the reaction between (1S,2R)-(+)-2-amino-1,2-diphenylethanol and phenyl isocyanate. This selector was immobilized on aminated silica gel, respectively, with bifunctional group linkers of 1,4-phenylene diisocyanate, methylene-di-p-phenyl diisocyanate, and terephthaloyl chloride to produce corresponding three chiral stationary phases. The prepared compounds and chiral stationary phases were characterized by FT-IR, elemental analysis, (1)H NMR, and solid-state (1)H NMR. The enantioseparation ability of these chiral stationary phases was evaluated with structurally various chiral compounds. The chiral stationary phase prepared with 1,4-phenylene diisocyanate as linker showed excellent enantioseparation ability. The influence of different linkages on the enantioseparation was discussed.

Synthesis of dendritic stationary phases with surface-bonded L-phenylalanine derivate as chiral selector and their evaluation in HPLC resolution of racemic compounds.

Four dendrimers were synthesized on aminopropyl-modified silica gel using methyl acrylate and ethylene diamine as building blocks by divergent method. Four generations of chiral stationary phases (CSPs) were prepared by coupling of L-2-(p-toluenesulfonamido)-3-phenylpropionyl chloride to corresponding dendrimers. The derivatives prepared on silica gel were characterized by FT-IR, (1)H NMR, and elemental analysis. The selector loadings of these four generations of CSPs generally showed a decrease tendency with the increase of generation numbers of dendrimers. The enantioseparation properties of these CSPs were preliminarily investigated by high-performance liquid chromatography. The CSP derived from the three-generation dendrimer exhibited the best enantioseparation capability. Effects of the mobile phase composition and molecular structures of racemic mixtures on enantioseparation were further studied.

Synthesis of polymer-type chiral stationary phases and their enantioseparation evaluation by high-performance liquid chromatography.

Two new chiral polymers of different molecular weights were synthesized by the copolymerization of (1R,2R)-(+)-1,2-diphenylethylenediamine, phenyl diisocyanate and terephthaloyl chloride. The polymers were immobilized on aminated silica gel to afford two chiral stationary phases. The polymers and the corresponding chiral stationary phases were characterized by Fourier transform-IR, elemental analysis, 1H and 13C NMR. The surface coverages of chiral structural units on the chiral stationary phases were estimated as 0.27 and 0.39 mmol/g, respectively. The enantioseparation ability of these chiral stationary phases was evaluated with a variety of chiral compounds by high-performance liquid chromatography. The effects of the organic additives, the composition of mobile phases, and the injection amount of sample on enantioseparation were investigated. A comparison of enantioseparation ability between these two chiral stationary phases was made. It was believed that the chain length of polymeric chiral selector significantly affected the enantioseparation ability of corresponding chiral stationary phase.